1. Field of the Invention
The present invention relates to a near-field light generating element that records and plays a variety of information on a magnetic recording medium using a near-field light with focused light flux, a method of manufacturing a near-field light generating element, a near-field light head, a method of manufacturing a near-field, light head, and an information recording and playback device.
2. Background Art
In recent years, along with an increase in the capacity of a hard disk or the like in computer equipment, the recording density of information in a single recording surface has increased. For example, in order to increase the recording capacity of a magnetic disk per unit area, there is a need to increase the surface recording density. Incidentally, as the recording density increases, the recording area occupied per bit on the recording medium is reduced. When the bit size is reduced, energy held by one bit of information comes close to the heat energy of room temperature, whereby there is a problem of thermal demagnetization in which the recorded information is reversed or disappears owing to thermal fluctuations or the like.
Although the in-plane recording method generally used is a method of recording the magnetism so that a direction of magnetization faces the in-plane direction of the recording medium, in this method, the recording information is easily lost due to the thermal demagnetization mentioned above. Thus, in order to solve the disadvantage, in recent years, a perpendicular recording method is adopted in which a magnetization signal is recorded in a direction perpendicular to the recording medium. This method is to record the magnetic information using the principle of causing a single magnetic pole to approach the recording medium. According to this method, the recording magnetic field faces a direction that is substantially perpendicular to a recording film. Since N-pole and S-pole are difficult to make form a loop within the recording film surface, information recorded in the vertical magnetic field easily maintains energetic stability. For that reason, the perpendicular recording method becomes resistant to the thermal demagnetization compared to the in-plane recording method.
However, recent recording media require further increasing high densities in response to the needs for performing the recording and playback of larger amounts and higher densities of information, or the like. For that reason, in order to suppress the influence between the adjacent magnetic domains or the thermal fluctuations to the minimum, one having strong coercive force is begun to be adopted as the recording medium. For that reason, even in the perpendicular recording method mentioned above, it is difficult to record information on the recording medium.
Thus, in order to solve the disadvantage mentioned above, a hybrid magnetic recording-type recording and playback head is provided in which the magnetic domain is locally heated using a spot light with the focused light or the near-field light to temporarily lower the coercive force, thereby performing the writing onto the recording medium in the meanwhile.
Among such recording and playback heads, a recording and playback head (hereinafter, referred to as near-field light head) using the near-field light mainly includes a slider, a recording element having a main magnetic pole and an return pole that are placed on the slider, a near-field light generating element that generates the near-field light from the irradiate laser light, a laser light source that irradiates laser light toward the near-field light generating element, and an optical waveguide that guides laser light generated from the laser light source to the near-field light generating element (for example, JP-A-2008-152897). The near-field light generating element has a core that propagates laser light while reflecting the same, a light flux propagation element having a cladding that comes into close contact with the core and seals the core, and a metal film that is placed between the core and the cladding to generate the near-field light from the laser light. The core is drawn so that the cross-sectional area perpendicular to the propagation direction of laser light facing from one end side (light incident side) to the other end side (light emission side) is gradually reduced, and is configured so as to propagate the laser light toward the other end side while focusing the same. Moreover, the metal film mentioned above is placed on a side surface of the other end side in the core.
In the case of using the near-field light head configured in this manner, a variety of information is recorded on the recording medium by generating the near-field light and applying the recording magnetic field. That is, laser light emitted from the laser light source is incident to the light flux propagation element via the optical waveguide. Moreover, laser light incident to the light flux propagation element is propagated through the cores and reaches the metal film. Then, since free electron within the metal film is uniformly vibrated by laser light, plasmon is excited and generates the near-field light on the other end side of the core in the state of being localized. As a result, the magnetic recording layer of the magnetic recording medium is locally heated by the near-field light and coercive force is temporarily lowered.
Furthermore, by providing the driving electric current to the recording element simultaneously with the irradiation of the laser light mentioned above, the recording magnetic field is locally applied to the magnetic recording layer of the magnetic recording medium adjacent to the tip of the main magnetic pole. As a result, it is possible to record a variety of information on the magnetic recording layer in which the coercive force is temporarily lowered. That is, by the cooperation of the near-field light with magnetic field, the recording to the magnetic recording medium can be performed.
However, in order to promote new high density of the recording medium, there is a need to reduce a spot size of the near-field light and more locally heat the magnetic recording layer of the magnetic recording medium, thereby suppressing the influence of the thermal fluctuation phenomenon mentioned above or the like. In order to reduce the spot size of the near-field light, a reduction in the width (width of the interface between the metal film and the core when viewed from the propagation direction of laser light) of the metal film is considered.
In this case, in the related art, since the core is formed according to the width of the metal film, the width (a width of an interface between the core and the metal film when viewed from the propagation direction of laser light) of the core is reduced along with the reduction in metal film.
However, when reducing the width of the core, the loss of the laser light propagated through the core is increased, whereby there is a problem in that a sufficient amount of light cannot be obtained. That is, the spot size of the near-field light can be reduced, but the amount of light is lowered.